The horrific Connecticut shootings are likely to change the tone of Congress’ debate over gun control and other efforts to curb violence.

But don’t look for big changes in those laws.

The Friday massacre of 26 people, including 20 children, at Sandy Hook Elementary School has shaken lawmakers like few events in recent years. Its emotional impact is comparable in recent years only to the attempted 2011assassination of Rep. Gabrielle Giffords, D-Ariz., but this incident has been even more jarring to members of Congress and the political world.

History shows that shocks like this often result in incremental changes to gun-control laws but little more, as fierce lobbying and political concerns become paramount.

The failures to achieve major changes are mired in the kind of politics that has stifled action on controversial gun-control measures for years. The nation remains divided over how or whether to regulate firearms, and the gun lobby remains one of the Capitol’s most powerful.

The National Rifle Association alone spent more than 10 times as much as gun-control groups on lobbying last year and in the first nine months of this year, according to data compiled by the nonpartisan Center for Responsive Politics.

The center found that last year was the most active election cycle in a dozen years for gun interest groups, as they gave $3 million to candidates, 96 percent of them Republicans, through mid-October. Gun-control groups barely registered, giving only $4,000, all to Democrats.

The gun lobby was unrelenting Monday. Eric Pratt, spokesman for Gun Owners of America, said if there’s to be a discussion on gun legislation it “should lead to a greater ability to protect one’s self. . . . Sadly, they (gun-control advocates) will try to exploit this to make people less safe.”

Some Republicans agreed. Said Rep. Louie Gohmert, R-Texas: “I wish to God she (the Sandy Hook principal) had had an M-4 (rifle) in her office,” so she could have taken it out and “takes his head off before he can kill those precious kids.”

Democrats countered with quick calls for gun-control action.

“We should stop making emotional room in our hearts for each year’s new round of public shootings and killing sprees,” said Rep. Raul Grijalva, D-Ariz.

Monday, though, two developments gave gun-control advocates new hope. Many Democrats, including President Barack Obama, who for years have been reluctant to speak out for tougher gun laws, aren’t holding back.

“I actually think things could change. The terrible nature of this shooting has the potential to transform the national debate,” said Darrell West, vice president and director of governance studies at Washington’s Brookings Institution.

There were some signs Monday that was occurring. “This has changed the dialogue, and it should move beyond the dialogue. We need action,” Sen. Joe Manchin, D-W.Va., an avid hunter, said on MSNBC’s “Morning Joe.”

Getting results, though, won’t be easy.

“I think that between election results and court decisions that a consensus has been settled on both sides that gun control is a non-starter,” said Keith Appell, a Virginia-based Republican strategist.

Appell said the Connecticut shooting will prompt gun-control advocates to produce legislation, “but it probably will not result in anything.”

Some Republicans steered their comments toward the problems of mental illness rather than gun violence.

“We must focus on the root cause of such disasters and not the means by which they enact their despicable deeds,” said Rep. Renee Ellmers, R-N.C., in a prepared statement.

Among those urging quick action was Sen. Dianne Feinstein, D-Calif., architect of a 1994 assault weapons ban in the wake of a 1989 elementary school shooting in Stockton, Calif., that left five students dead and 29 others and a teacher wounded. That ban expired in 2004, and Feinstein plans to mount a new effort.

Also pushing will be Rep. Carolyn McCarthy, D-N.Y., whose husband was killed during a mass shooting on the Long Island Railroad in 1993. She urged strengthening of background checks for gun buyers.

Lawmakers also renewed their pleas to tone down media violence. For years, Sen. Joe Lieberman, a Connecticut independent, and his allies have called attention at this time of year to entertainment violence. In the wake of the Connecticut tragedy, Lieberman wants a national commission to study the matter.

“It doesn’t make everybody more violent. But it’s a causative factor in some cases,” he told Fox News. “We’ve got to ask the entertainment industry, ‘What are you going to do to try to tone that down?’”

They have some political wind behind them.

“In the coming days and weeks, we will engage in a meaningful conversation and thoughtful debate about how to change laws and culture that allow violence to grow,” Senate Majority Leader Harry Reid, D-Nev., vowed Monday.

Rupert Murdoch, whose News Corp. owns conservative Fox News, tweeted, “When will politicians find courage to ban automatic weapons?” New York City Mayor Michael Bloomberg this fall launched his Independence USA political action committee to support political candidates who share his views on several subjects, including tougher gun laws.

But advocates face daunting opposition and skepticism. A Washington Post-Kaiser Family Foundation poll this summer, after a mass shooting at an Aurora, Colo., movie theater, found only 51 percent of respondents favored stricter gun-control laws, while 47 percent were opposed. A CNN/ORC survey taken around the same time said 57 percent favored a ban on the manufacture, sale and possession of semiautomatic assault weapons, such as the AK-47, while 42 percent were opposed.

One of the last major pushes for gun control came in 1999, one month after the nation was stunned by the shootings at Columbine High School in Colorado, in which two heavily armed students killed 12 fellow students and a teacher and injured nearly two dozen others before committing suicide.

As part of a juvenile justice bill, Democrats pushed a plan to require background checks at gun shows and pawn shops. The vote in the Senate was a 50-50 tie, with Vice President Al Gore breaking the tie and allowing the change to pass.

The vote became political mythology – that Gore’s decision cost him valuable votes in his 2000 presidential bid, chilling gun-control talk by future Democratic White House hopefuls. Not only are longtime gun-control supporters ready to fight, perhaps with Obama’s help, but Republicans are in some disarray.

“The 2012 election shows Republicans need to reposition themselves,” said West of the Brookings Institution. As the party struggles to broaden its appeal, gun control could become attractive for certain Republicans.

So far, though, the evidence is scant. Sunday network talk shows reached out to key Republicans, but few were eager to talk.

“We tried to get a Republican from the Judiciary Committee” said Bob Schieffer, moderator of CBS’ “Face the Nation,” “but all of the members were either unavailable or said no.”